1. Field of the Invention
The present invention relates to a method and apparatus for filling molds and especially molds of an intricate shape with nonflowing molding materials, particularly comminuted organic fibrous materials which are mixed with suitable binders, for example, heat-setting synthetic resins.
2. Description of the Prior Art
Prior to this invention, molds of this type have usually been filled by hand. This had, however, the disadvantage that even the operation of filling molds of a relatively simple shape required a considerable length of time and that it was practically impossible to distribute the molding mixture in the mold so as to have the desired uniform density at all points.
Mechanical filling devices for such molds have also been developed wherein the molding material after passing through an arrangement of rotating spiked rollers is filled at a steady rate through a funnel into the mold. By making these spiked rollers of a suitable design and dimensions, by providing them in a suitable arrangement and driving them at a suitable speed, it is possible to treat the molding material to a certain extent in accordance with its different layer thicknesses so as to attain a substantially homogeneous molded body. Although this method may be satisfactory for properly filling molds of a simple shape, it does not produce any satisfactory results if the molds are of an intricate shape, since it may often occur that the molding mixture will not pass with the required uniform density into more remote and difficultly accessible parts of such a mold. Furthermore, the mechanical effort of carrying out this method and the expense for the necessary apparatus, as well as the amount of space such apparatus requires, are very considerable.
Attempts have also been made to attain a uniform filling of the mold by vibration, shaking or jarring. These methods and especially that of vibrating the mold are, however, applicable only to lighter molds and hardly, if at all, to large and heavy molds. Furthermore, especially when applying the vibration method, vibration nodes will occur which cause the molding material to settle into certain shapes. Shaking and vibrating a mold also result in a separating effect whereby the coarser and finer particles become more or less separated from each other or are sorted according to their degree of fineness. The material will then either be distributed in accordance with the shapes caused by the vibration nodes or the coarse particles will be brought up to the upper surface of the mold. Particularly the last-mentioned effect is, however, very undesirable if the molded bodies should have the smoothest possible outer surface, for example, for being provided with a decorative coating.